Corrosion inhibition



3,ll4,?2 Fatented Dec. 17, 11%63 Oil Products Company, Des Plaines, Ill, a corporation of Delaware No Drawing. Fiiezl Jan. 18, 195%, Ser. No. 2,311 13 Claims. (Cl. 253-348) This invention relates to a novel method of inhibiting corrosion of metal surfaces.

In the handling of various organic materials, particularly hydrocarbons, it is often necessary to transport, store and/or use such materials in metal containers as, for example, in steel, iron, copper, Admiralty metal, zinc, tin, or other metal pipe lines, drums, tanks, etc. Since these materials often contain varying amounts of acidic corrodants including, for example, hydrogen chloride, hydrogen sulfide, carbon dioxide, etc., internal corrosion occurs in the presence of water which invariably also is present. The corrosion problem is encountered in the handling of gasoline, naphtha, kerosene, fuel oil, lubricating oil, residual oil, crude oil, etc. Corrosion problems are encountered with other oils including railroad oils, aircraft oils, instrument oils, insulation oils, cutting oils, soluble oils, rolling oils, the latter comprising oils used in the rolling of metals and other forming operations such as stamping, cutting, casting, etc. These oils may be of mineral, animal or vegetable origin. Corrosion problems also occur in the handling of various lubricating and coating compositions such as greases, both of synthetic and of petroleum origin, waxes, household oils, paints, lacquers, etc.

The novel inhibitors of the present invention are of especial utility for use under anaerobic conditions; that is, in atmospheres substantially free of oxygen. These anaerobic conditions occur in the processing of hydrocarbons, for example, in which the hydrocarbons are heated, processed and fractionated at elevated temperature and superatmospheric pressure in plant equipment of airtight construction. An example of such anaerobic conditions is in the case of a stabilizing column used to strip lighter components from the reaction products of a reforming operation. In the reforming operation, a gasoline or naphtha is subjected to contact with a reformin catalyst at a temperature of from about 800 to about 950 F. in the presence of hydrogen. Any suitable reforming catalyst is used and preferably comprises a composite containing platinum, more particularly an alumina-platinum composite and still more particularly an alumina-platinum-combined halogen composite. Other reforming catalysts include composites containing metals or compounds of metals in the left-hand columns of groups V, VI and VIII of the periodic table. Specific composites in this class are alumina-molybdenum oxide, alumina-molybdenum oxide-cobalt oxide, alumina-molybdenum oxide-nickel oxide, alumina-palladium, aluminapalladium oxide, etc., as well as the corresponding sulfides thereof. The charge to reforming may be a full boiling range gasoline or a selected cut thereof, referred to as naphtha and having an initial boiling point within the range of from about 150 to about 350 F. and an end boiling point from about 325 to about 450 F. The reactor efiluent products are cooled to separate hydrogen for reuse in the process, and the liquid products are subjected to stabilization to strip lighter components therefrom. The lighter components removed as an overhead from the stabilizing column contains acidic components, in this case particularly HCl, which then are passed through cooling equipment in order to condense liquid components. The charge to the stabilizer contains water and, upon cooling of the hot efiluent products from the stabilizer, corrosion occurs in the cooling and receiving equipment. The cooling equipment is generally of the heat exchange type, in which the hot efiluent overhead products from the stabilizer are passed in indirect heat exchange with a heat exchange medium of lower temperature. Considerable difiiculty is encountered because of corrosion of the heat exchanger and the resultant necessity of replacing the internal equipment thereof. This in turn necessitates shutting down the stabilizer and, as can be seen, interferes with continuous plant operation.

Another example of corrosion problems encountered in plant equipment is in the prefractionation of a petroleum charge to separate the same into a selected fraction or fractions for subsequent catalytic conversion. For example, a gasoline fraction may be subjected to fractionation to separate an intermediate or high boiling fraction for use as charge to a reforming operation of the type hereinbefore described. The fraction subjected to such separation contains acidic components and Water and, upon cooling of the overhead products, corrosion of the cooling and receiving equipment occurs. This problem is acute and, as mentioned above, it results in too frequent shut-downs to replace the internals of the heat exchangers, the connecting piping and/0r receiver, and necessitates discontinuing the prefractionator operation.

The above are two examples in which serious corrosion problems are encountered upon cooling of the hot efiluent products of a distillation zone. The term distillation zone is used in the generic sense to include any type of fractionation, stripping, stabilization, etc. in which the overhead effluent products are subjected to cooling to separate a condensate. In most cases at least a portion of the condensate is recycled to the upper portion of the distillation zone as a cooling and refluxing medium therein.

While the novel process of the present invention is particularly applicable in reducing corrosion of plant equipment under anaerobic conditions, it is understood that the invention also may be used for reducing corrosion in other applications. For example, the corrosion inhibitor of the present invention is useful to prevent corrosion in oil well operations, as pickling inhibitor for mineral acids, etc.

In the treatment of hydrocarbons or other oils, a particularly advantageous method of introducing a corrosion inhibitor is to incorporate the corrosion inhibitor in the hydrocarbon or other oil prior to distillation. It is a particular advantage of the present invention that the novel inhibitor is oil soluble and is readily incorporated in the hydrocarbon oil. In another embodiment the inhibitor of the present invention may be introduced directly into the distillation zone and will serve therein to protect the internal equipment of the distillation zone, such as bubble decks, bubble trays, side to side pans, etc. The inhibitor of the present invention is volatile and will be carried overhead, at least in par-t, with the lighter fracride with ammonia.

tions and thus also will serve to reduce corrosion of the overhead transfer line and heat exchangers during cooling of the hot overhead products. Furthermore, the inhibitor will carry into the settler, receiver, etc. and also will serve to prevent corrosion of these containers. Still another advantage of the novel inhibitor of the present invention is that it does not promote emulsification and accordingly will not cause such difiiculties during the separation of the hydrocarbon product in the settler, receiver, etc.

In one embodiment the present invention relates to a method of reducing corrosion of metal in contact with an acidic corrodant which comprises effecting said contact in the presence of a corrosion inhibitor having the folwhere R and R are alkyl groups, R and R are alkylene groups joined to the nitrogens through a straight chain of 2 to 4 carbon atoms, x is an integer from 0 to 3, and R is selected from the group consisting of hydrogen and RGH In a specific embodiment the present invention relates to a method of reducing corrosion of plant equipment upon cooling of hot efiluent products from a distillation Zone and avoiding emulsification during subsequent separation, which comprises incorporating N ,N -di-(1-ethyl- 3-methylpentyl) diethylene triamine in said hot efiluent products, subsequently cooling said hot eflluent products, and thereafter separating an oil phase from an aqueous phase.

From the general formula hereinbefore set forth, it will be noted that the novel inhibitor of the present invention contains a secondary alkyl configuration attached to one or more nitrogen atoms and that it also contains from 2 to 4 carbon atoms between the nitrogen atoms. The novel inhibitors of the present invention are prepared economically by the reductive alkylation of an alkylene polyamine with a ketone. It is an essential feature of the present invention that the inhibitor contains at least one secondary alkyl group attached to a nitrogen atom and preferably at least two of such attachments.

Any suitable alkylene polyamine is used in preparing the inhibitor of the present invention. Diethylene triamine is particularly preferred. Other alkylene polyp amines include ethylene diamine, triethylene tetramine, tetraethylene pentamine, etc. Other alkylene polyamines include propylene diamine (1,3-diaminopropane), dipropylene triamine, tripropylene tetramine, tetrapropylene pentamine, etc., butylene diamine (1,4-diaminobutane),

dibutylene triamine, tributylene tetramine and tetrabutylene pentamine. As hereinbefore set forth, the alkylene group joined to the nitrogen atoms contains from 2 to 4 carbon atoms. It is understood that the alkylene group may contain other substituents and particularly hydrocarbon and still more particularly alkyl groups attached thereto as, for example, in such compounds as 1, 2-diaminopropane, 1,3-diaminobutane, etc. It is understood that the various alkylene polyamines are not necessarily equivalent and also that a mixture of alkylene polyamines may be utilized. In some cases, the higher boiling alkylene polyamines may contain some cyclic amines, such as piperazines. However, satisfactory inhibitors are produced from such mixtures.

As another advantage of the present invention, the alkylene polyamine may comprise the polyamine residue remaining after distilling off lighter products in the manufacture of ethylene diamine.

Ethylene diamine is prepared by reacting ethylene chlo- During the reaction, products boiling above ethylene diamine are inherently produced. In the recovery of the products from the ethylene diamine manufacture, ethylene diamine, diethylene triamine, triethylene tetramine and tetraethylene pentamine are distilled off and further separated to recover the individual polyamines as substantially pure chemical products. Remaining higher boiling products are recovered as a residue and may be used in preparing the corrosion inhibitor of the present invention. This polyamine residue is available commercially from a number of sources. One example is Amine E100 sold by the Dow Chemical Company. This polyamine residue has a specific gravity at 77/77 F. of 0956-0962 and a boiling range at 760 of 5% at 381 F. and of 80% at 437 F. A similar polyamine residue is available from Carbide & Carbon as Polyamine H Special. In some cases a lighter polyalkylenepolyamine, particularly diethylene triamine and/ or triethylene tetramine, is blended with the polyamine residue in small amounts, say from about 1% to about 15% by weight, in order to reduce the viscosity and to facilitate pumping and handling thereof. This may serve to increase the specific gravity at 77/77 F. to about 0.999 or slightly higher.

The ketone for use in the reductive alkylation will be selected with reference to the alkylene polyamine in order that the inhibitor is oil soluble. Accordingly, with ethylene diamine and diethylene triamine, the ketone may contain as low as 3 carbon atoms. On the other hand, with triethylene tetramine or tetraethylene pentamine, the ketone should contain at least 8 carbon atoms.

Particularly preferred ketones for use in the reductive alkylation step include methyl hexyl ketone and ethyl amyl ketone. Other ketones which may be used, while bearing in mind the limitations mentioned above, include acetone, methyl ethyl ketone, methyl propyl ketone, methyl butyl ketone, methyl amyl ketone, methyl heptyl ketone, methyl octyl ketone, methyl nonyl ketone, methyl decyl ketone, methyl undecyl ketone, methyl dodecyl ketone, methyl tridecyl ketone, methyl tetradecyl ketone, methyl pentadecyl ketone, methyl hexadecyl ketone, methyl heptadecyl ketone, methyl octadecyl ketone, methyl nonadecyl ketone, methyl eicosyl ketone, etc., diethyl ketone, ethyl propyl ketone, ethyl butyl ketone, ethyl hexyl ketone, ethyl heptyl ketone, ethyl octyl ketone, ethyl nonyl ketone, ethyl decyl ketone, ethyl undecyl ketone, ethyl dodecyl ketone, ethyl tridecyl ketone, ethyl tetra- .decyi ketone, ethyl pentadecyl ketone, ethyl hexadecyl ketone, ethyl heptadecyl ketone, ethyl octadecyl ketone, ethyl nonadecyl ketone, ethyl eicosyl ketone, etc., dipropyl ketone, propyl butyl ketone, propyl amyl ketone, propyl hexyl ketone, propyl heptyl ketone, propyl octyl ketone, propyl nonyl ketone, propyl decyl ketone, propyl undecyl ketone, propyl dodecyl ketone, propyl tridecyl ketone, propyl tetradecyl ketone, propyl pentadecyl ketone, propyl hexadecyl ketone, propyl heptadecyl ketone, propyl octadecyl ketone, propyl nonadecyl ketone, propyl eicosyl ketone, etc., diamyl ketone, dihexyl ketone, diheptyl ketone, dioctyl ketone, dinonyl ketone, didecyl ketone, diundecyl ketone, didodecyl ketone, ditridecyl ketone, ditetradecyl ketone, dipentadecyl ketone, dihexadecyl ketone, diheptadecyl ketone, dioctadecyl ketone, dinonadecyl ketone, dieicosyl ketone, etc.

In general the number of carbon atoms in the ketone will not exceed about 40. A number of ketones containing at least 12 carbon atoms are available as mixtures which are either products or by-products of commercial operations. These mixtures generally are available at lower cost and, as another advantage of the present invention, the mixtures may be used without the added time and expense of separating specific compounds in pure state. An example of such a mixture available commercially is Stearone, which consists primarily of diheptadecyl ketone.

Referring again to the general formula hcreinbefore set forth, R and R may be either of straight carbon chain or may contain branching in the chain. A preferred ketone for use in the reductive alkylation is one in which R contains a methyl group attached to the second carbon atom as in ethyl Z-methyl butyl ketone. While the alkyl groups are preferred, in some cases R and/or R may contain an unsaturation in the chain, particularly where R or R contains 12 or more carbon atoms. In some cases these ketones are derived from unsaturated fatty acids and thus contain unsaturation in the chain. While generally it is preferred to utilize the same ketone in forming the inhibitor, it is understood that a mixture of ketones may be employed. Also, it is understood that the different ketones are not necessarily equivalent for use in preparing the reductive alkylation product but all will serve to produce a corrosion inhibitor which is effective in at least some applications.

The ketone and alkylenepolyamine are subjected to reductive alkylation to produce the corrosion inhibitor for use in the present invention. The reductive alkylation is effected readily at a temperature of from about 200 to about 500 F. and a pressure of from about 100 to 3000 pounds or more per square inch. Hydrogen is utilized in a concentration of at least one mole of hydrogen per mole of alkylenepolyamine. Generally however, it is preferred to operate with a molar excess of hydrogen over that required stoichiometrically. Any suitable catalyst may be used in the reductive alkylation process including nickel, platinum, palladium, etc., preferably cornposited with a suitable support. A particularly preferred catalyst comprises a composite of platinum and alumina, which may or may not contain combined halogen. The platinum generally is present in the catalyst in a concentration of from about 9.1% to about 2% by Weight of the final catalyst and the halogen, when present, is in a concentration of total halogen of from about 0.01% to about 1% by weight of the final catalyst, the halogen preferably comprising fluorine and/ or chlorine. A pre ferred nickel catalyst is a composite of nickel and kieselguhr containing from about 30% to about 60% by weight of nickel. It is understood that the platinum or nickel may be present as the free metal and/ or compounds thereof. Another preferred catalyst includes a composite of copper oxide, chromium oxide and barium oxide. These catalysts are well known in the art and need not be described in detail in the present application because no novelty is being claimed herein for the catalyst per se. When desired, the reductive alkylation may be effected in the presence of a solvent. Any suitable solvent may be utilized and may comprise, for example, a hydrocarbon including benzene, cumene, toluene, ethylbenzene, decalin, etc.

In general, it is preferred to efiect the reductive alkylation in one step, in the presence of hydrogen as hereinbefore described. However, in some cases, the reaction may be effected in two steps. In the first step, the reaction is effected in the absence of hydrogen to produce the corresponding Schiifs base and thereafter the Schiffs base is hydrogenated. Substantially the same conditions and catalysts are used as hereinbefore set forth, except that the first step is effected in the absence of hydrogen and water formed in the first step is removed prior to the second step.

A preferred reductive alkylation product for use in the present invention is prepared by the reductive alkylation of diethylene triamine with ethyl amyl ketone to form N ,N -di-(1-ethyl-3 -methylpentyl) diethylene triamine. Another preferred inhibitor is prepared by the reductive alkylation of ethylene diamine and methyl hexyl ketone to form N,N-di-(1-methylheptyl) ethylene diamine. Another inhibitor is N ,N -di-(1-ethyl-3-methylpentyl) tetraethylene pentamine prepared by the reductive alkylation of tetraethylene pentamine with ethyl amyl ketone. As hereinbefore set forth, numerous inhibitor compounds are prepared by the reductive alkylation of the alkylenepolyamine and ketone, the specific product depending upon the particular alkylenepolyamine and ketone used in the reductive alkylation. Additional illustrative examples of inhibitors include N,N'-di-(l-methylethyl) ethylene diamine, N ,N di (1 methylethyl) diethylene triamine, N ,N -di-(1-methylethyl) triethylene tetramine, N ,N di-(l-methylethyl) tetraethylene pentamine, etc., N,N'- di-(l-methylpropyl) ethylene diamine, N ,N -di-(1-methylpropyl) diethylene triamine, N ,N -di-(l-methylpropyl) triethylene tetramine, N ,N -di-(1-methylpropyl) tetraethylene pentamine, etc., N,N-di-(1-methylbutyl) ethylene diamine, N ,N -di (1 methylbutyl) diethylene triamine, N ,N -di (1 methylbutyl) triethylene tetramine, N ,N -di-(1-methylbutyl) tetraethylene pentamine, etc., N,N-di-(l-methylpentyl) ethylene diamine, N ,N -di-(1- methylpentyl) diethylene triamine, N ,N -di-(1-methylpentyl) triethylene tetramine, N ,N -di-(l-methylpentyl) tetraethylene pentamine, etc., N,N'-di (1 methylhexyl) ethylene diamine, N ,N -di (1 methylhexyl) diethylene triamine, N ,N -di-(l-methylhexyl) triethylene tetramine, N ,N -di-(l-methylhexyl) tetraethylene pentamine, etc., N ,N -di(l-methylheptyl) diethylene triamine, N ,N -dil methylheptyl) triethylene tetramine, N ,N di 1- methylheptyl) tetraethylene pentamine, etc., N,N'-di-(1- methyloctyl) ethylene diamine, N ,N -di-(1-methyloctyl) diethylene triamine, N ,N -di-(1-methyloctyl) triethylene tetramine, N ,N -di-(l-methyloctyl) tetraethylene pentamine, etc., N,N'-di-(1-ethyl-3-methylpentyl) ethylene diamine, N ,N -di-(1-ethyl-3-methylpentyl) triethylene tetramine, etc., N,N-di-(l-heptadecyl) ethylene diamine, N ,N -di-( l-heptadecyl) diethylene triamine, N ,N -di-(1- heptadecyl) triethylene tetramine, N ,N -di(l-heptadecyl) tetraethylene pentamine, etc., N,N'-di-(l-octadecyl) ethylene diamine, N ,N -di-(1-octadecyl) diethylene triamine, N ,N di (l octadecyl) triethylene tetramine, N ,N di (1 octadecyl) tetraethylene pentamine, etc. While the dialkylated products are preferred, in some cases the monoalkylated or trior higher alkylated products may be employed, either alone or in admixture with the dialkylated products. Illustrative monoalkylated products include N-(l-methylheptyl) ethylene diamine, N-(l-methylheptyl) diethylene triamine, N- (l-methylheptyl) triethylene tetramine, etc., N-(l-ethyl-B-methylpentyl) ethylene diamine, N (1 ethyl-3-methylpentyl) diethylene triamine, N-(1-ethyl-3-methylpentyl) triethylene tetramine, etc. Illustrative polyalkylated products include N ,N ,N -tri-(l-methylethyl) diethylene triamine, N ,N ,N -tri-(1-methylethyl) triethylene tetramine, N N ,N ,N -tetra-(l-rnethylethyl) triethylene tetramine, N N ,N -tri-(l-methylethyl) tetraethylene pentamine, N N ,N ,N ,N -penta-(1 methylethyl) tetraethylene pentamine, etc. It is understood that the specific compounds recited above are merely illustrative and that, as hereinbefore set forth, diiferent inhibitors are prepared by reacting diiferent ketones with different alkylenepolyamines. Also, as hereinbefore set forth, the various inhibitors are not necessarily equivalent in the same or different substrates but all of them will possess corrosion inhibiting properties.

The preferred reductive alkylation product is recovered as a non-viscous liquid which is readily soluble in hydrocarbon oil and may be marketed as such, thereby avoiding the use of a solvent. However, in some cases the use of a solvent is desired, particularly with some of the other reductive alkylation products which may be viscous or solid. Any suitable solvent may be employed. Conveniently, the solvent comprises the same solvent used in preparing the reductive alkylation product and is recovered in admixture with at least a portion of the solvent, thereby avoiding the necessity of removing all of the solvent and subsequently adding it back. When a more dilute solution is desired, it is understood that the same or different solvent may be commingled with the reductive alkylation product to form a solution of the desired concentration. As hereinbefore set forth, a hydrocarbon solvent and particularly those hereinbefore specifically recited is preferred. However, it is understood that other suitable solvents may be used including alcohols such as methanol, ethanol, propanol, butanol, etc., ketones such as acetone, methyl ethyl ketone, methyl propyl ketone, etc.

, The amount of inhibitor to be employed will depend upon the concentration of acidic components and the particular substrate in which the inhibitor is to be used. When used in plant equipment, the environment preferably is maintained at a pH of from about 5.5 to 7 by adding ammonia or the like and adding the inhibitor at a rate of 2 to 10 pounds per 1000 barrels of hydrocarbon stream. The inhibitor is believed to form a film over the metal and thereby protect it against corrosion. In general, the corrosion inhibitor, based on active ingredient, is used in a concentration of from about 0.00001% to about 1% and preferably from about 0.000170 to about 0.05% by weight of the substrate.

As hereinbefore set forth, the corrosion inhibitor may be incorporated directly into the substrate or it may be introduced directly into a distilling zone or into the overhead vapor products or side streams, if any, being withdrawn from the distilling zone. It is understood that the corrosion inhibitor of the present invention may be used along with other additives which are incorporated in the substrate for specific purposes including, for example, antioxidants, metal deactivators, dyes, etc., particularly when the corrosion inhibitor is added to a final product passing to storage.

The following examples are introduced to illustrate further the novelty and utility of the present invention but not with the intention of unduly limiting the same.

EXAMPLE I N ,N -di-(l-ethyl-3-methylpentyl) diethylene triamine was prepared by the reductive alkylation of diethylene triamine with ethyl amyl ketone. The reductive lalky-lation was efiected in two steps. Seventy grams (0.68 mole) of diethylene triamine and 268 grams (2.09 moles) of ethylene amyl ketone were heated to boiling under refluxing conditions until 26 ml. of water were collected. The mixture then was reacted at a temperature of 320 F., a maximum hydrogen pressure of about 1900 p.s.i.g. in contact with a reduced platinum catalyst comprising alumina composited with 0.3% by weight of platinum. The reductive alkylation product was distilled at about 2 mm. pressure to recover N ,N -di-(1-ethyl-3- methylpentyl) :diethylene triamine as a fluid brown liquid, having a boiling point of 140l70 C.

The inhibitor prepared as described above was evaluated as a corrosion inhibitor in the following manner. In this test a steel metal coupon of about x 6" x is suspended in the vapor space of a 1-liter flask containing 300 cc. of a heptane fraction and 100 cc. of corrosive water having a pH of 2.0, the flask being equipped with a reflux condenser at the top. Hydrogen sulfide is continuously introduced at a rate of 2.1.9 cc. per minute into the lower portion of the flask. The flask is maintained at a temperature of about 200 F. and the rising vapors, consisting of hydrocarbon and entrained water, pass over the test couplon, are collected at the top of the flask and the condensate passes downward over the test coupon at an average rate of 25 cc. per minute. The test is continued for 10 hours, after which the loss in weight due to corrosion is determined by weighing.

The following table reports the results of a run in the absence of a corrosion inhibitor and two runs in which different concentrations of the inhibitor prepared as described above are added to the hydrocarbon which passes over the test coupon. The inhibitor-hydrocarbon mixture is introduced at a rate of 1 cc. per minute. Because this test is run at 200 F., the inhibitor passes over the test coupon only once and is not volatilized to further contact the metal coupon as do the hydrocarbon and acidic vapors. Accordingly, the actual concentration of inhibitor contacting the test coupon is approximately of that of the inhibitor-hydrocarbon mixture. In one case the mixture contained 0.1% and in the other case 0.025% by weight of inhibitor.

From the data in the above table, it will be seen that the inhibitor of the present invention was very effective in retarding corrosion, even when used in an initial concentration as low as 0.025% by weight of the hydrocarbon.

EXAMPLE II It was of interest to determine whether the crude reductive alkylation product prepared in the manner as described in Example I could be used without final distilling of the reductive alkylation product to recover a selected fraction. In other words, economies are eifected if the crude reductive alkylation product could be used without the necessity of final distillation. Another preparation was made similar to that described in Example I except that the reductive alkylation product was not distilled but instead the excess ketone was removed merely by pumping in vacuum. As will be shown in the data in the following table, this product was an effective corrosion inhibitor and advantageously is utilized in accordance with the present invention.

The product prepared in the manner described above had the following physical properties:

Table II Flash point, F 315 Kinematic viscosity at 100, cst 9.017 Kinematic viscosity at 40, cst 54.84 Universal viscosity at 100, sec 55.6 Universal viscosity at 40, sec 253.3 Pour point, F 35 Density at 60 0.8640 Nitrogen, weight percent 13.2

From the above properties, it will be noted that the product has a low pour point and a high flash point. It is apparent that these properties are of extreme advantage in corrosion inhibitors. Furthermore, the product is volatile and therefore will be distributed throughout a distillation zone, rthus serving also to protect the internal equipment in the distillation zone against corrosion.

The inhibitor prepared in the above manner was evalurated as a corrosion inhibitor in substantially the same manner as described in Example I. The results of these From the data in the above table, it will be seen that the reductive alkylation product without final distillation also was eitective to retard corrosion, even in such low initial concentrations as 0.0125 by weight.

9 EXAMPLE III N ,N -di-(l-methylheptyl) diethylene triamine was prepared by the reductive alkylation of diethylene triarnine with methyl hexyl ketone in substantially the same manner as described in Example l. The results of this evaluation are shown in the following table, along with the results of an evaluation without added inhibitor.

Table IV Weight of Strip Inhibitor Loss,

Initial,

g. mg.

Final, g.

It will be noted that this inhibitor was effective in reducing corrosion.

EXAMPLE IV The inhibitor prepared in substantially the same manner as described in Example =1 also was evaluated as a corrosion inhibitor in the presence of hydrogen chloride. This evaluation was made as follows:

A freshly cleaned steel strip was placed in 200 cc. of l N hydrochloric acid and allowed to stand at room temperature for 48 hours. At the end of this time the test strip had lost more than one gram in weight. When the test was carried out for 72 hours using the acid containing 0.1% by volume of N ,N -di-(l-ethyl-3-methylpentyl) diethylene triamine, the loss in weight was 18 mg.

These results are shown in the following table. The inhibitor was used in a concentration of 0.1% by volume.

Table V Weight of Strip Inhibitor Hours Initial, g. Final,

Loss, mg.

None 0.1% by volume of the inhibitor inhibitor described in Example I EXAMPLE V Weight of Strip Inhibitor Initial, Final,

Loss, g. mg.

None 0.0l25% by weight of the inhibitor prepared in the above manner EXAMPLE VI As hereinbefore set forth, an effective inhibitor is prepared when using the polyamine bottoms remaining in the manufacture of ethylene diamine. This product was reductively alkylated with ethyl amyl ketone in substantially the same manner as described in Example I. The results of these evaluations are reported in the following table:

Table VII Weight of Strip Inhibitor Initial, Final, Loss,

1;- gmg.

None 8.3597 8. 8417 18.0 0.015% by weight of the reductive a1- kylation product prepared as described above 7. 5450 7. 5425 2. 5

EXAMPLE Vl'I As hereinbefore set forth, another advantage to the corrosion inhibitor of the present invention is that it does not cause iemulsiiication and thus will not interfere with the separation of the hydrocarbon and aqueous phases in the settler or receiver. The emulsification was evaluated in the following manner.

-A heptane fraction cc.) containing pants per million of the inhibitor was shaken with 20 cc. of tap Water in a 100 cc. glass stoppered graduate for 2 minutes and then allowed to stand undisturbed for 5 minutes. The amount of emulsion was then evaluated visually. The test was repeated using 10% and 20% sodium hydroxide instead of the tap water. When evaluated in the above manner, the interface in all cases was very clean and showed no emulsion.

EXAMPLE VIH As hereinbe-fore set forth, the corrosion inhibitor of the present invention is particularly applicable in retarding corrosion of plant equipment. This is illustrated in the pnesent example in which the corrosion inhibitor of the present invention is commingled with reformed naphtha being passed from a receiver to a stabilizer for removal of light components. The reforming was effected in substantially the same manner as hereinbefore described. The liquid passing to the stabilizer contains acidic corrodants, particularly H61 and H 8, as well as water. The corrosion inhibitor is added to the liquid passing to the stabilizer in a concentration of 0.001% by weight of the liquid passing to the stabilizer. The corrosion inhibitor is :N ,N -di(l-ethyl-3-methylpentyl) diethylene triamine. In the stabilizer the corrosion inhibitor is distributed throughout the stabilizer and serves to reduce corrosion of the internal equipment therein. A portion of the corrosion inhibitor is carried ovenhead in the vapors and serves to reduce corrosion of the transfer line and con necting heat exchangers and receiver. A portion of the condensate from the receiver is recycled as a refluxing medium to the upper portion of the stabilizer. Part of the corrosion inhibitor remains in the naphtha being withdrawn from the bottom of the stabilizer and serves to reduce corrosion of the cooling and collecting equipment through and into which the naphtha is passed.

I claim as my invention:

1. A method of reducing corrosion of metal in contact with an acidic oorrodant which comprises effecting said contact in the presence of a corrosion inhibitor selected from the group consisting of N ,N -di-(l-ethyl-3-methylpentyl) diethylene triarnine, N,N'-di-(l-ethyl-3-methylpentyl) ethylene diamine, N ,N di (1 ethyl-3-rnethylpentyl) tetraethylene pentamine, N,N' di (1 methylheptyl) ethylene diamine and N ,N -di-(l-methylheptyl) diethylene triamine.

2. A method of reducing corrosion of metal in contact with a hydrocarbon and an acidic corrodant which comprises elfecting said contact under anaerobic conditions in the presence of a corrosion inhibitor selected from the group consisting of N ,N -di-(1-ethyl-3-methylpentyl) diethylene triamine, N,N' di (1 ethyl-3-methy1pentyl) ethylene diamine, N ,N -di-(l ethyl 3 methylpentyl) tetraethylene pentarnine, N,N di (1 methylheptyl ethylene diamine and N ,N -di-(l-methylheptyl) diethylene triamine.

1 1 s 3. The method of claim 2 further characterized in that said corrosion inhibitor is incorporated in said hydrocarbon in a concentration of from about 0.00001% to about 1% by Weight of said hydrocarbon prior to contact with said metal.

4. A method of reducing corrosion of metallic plant equipment in which a hydrocarbon material containing acidic corrodants is being processed, which comprises effecting said processing in the presence of a corrosion inhibiting amount of an inhibitor selected from the group consisting of N ,N di (l-ethyl-3-methylpentyl) diet'nylrpentarnine.

8. The process of claim 4 wherein said corrosion inhibitor is N,N-di-(1-methylheptyl) ethylene diamine.

9. The process of claim 4 wherein said corrosion inhibitor is N ,N -di-(l-methylheptyl) diethylene triamine,

10. The method of claim 2 further characterized in 12 that said hydrocarbon is being distilled in contact with said metal.

11. The method of claim 4 further characterized in that said corrosion inhibitor is dissolved in said hydrocarbon material prior .to the processing of the latter.

12. The method of claim 4 further characterized in that the processing of said hydrocarbon material includes a fractionating step.

13. A process for fractionating a hydrocarbon mixture in metallic plant equipment, said mixture containing H 6 and an acidic component having a corrosive effect on the metal of said equipment, which comprises distilling the hydrocarbon mixture under anaerobic conditions in the presence of a corrosion inhibiting amount of N ,N di(l ethyl-3 methylpentyl) di-ethylene-triamine.

References Cited in the file of this patent UNITED STATES PATENTS 2,028,041 Bersworth Jan. 14, 1936 2,152,720 Yabroif Apr. 4, 1939 2,818,388 Sullivan et al Dec. 31, 19 7 2,856,299 Westlund Oct. 14 ,1958 2,911,351 Hill Nov. 3, 1959 2,913,305 Andersen Nov. 17, 1959 2,920,030 Thompson Jan. 5, 1960 2,924,571 Hughes Feb. 9, 1960 2,938,851 Stedman et al May 31, 1960 

1. A METHOD OF REDUCING CORROSION OF METAL IN CONTACT WITH AN ACIDIC CORRODANT WHICH COMPRISES EFFECTING SAID CONTACT IN THE PRESENCE OF A CORROSION INHIBITOR SELECTED FROM THE GROUP CONSISTING OF N1,N3-DI-(1-ETHYL-3-METHYLPENTYL) DIETHYLENE TRIAMINE, N,N''-DI-(1-ETHYL-3-METHYLPENTYL) ETHYLENE DIAMINE, N1,N5 - DI - (1-ETHYL-3-METHYLPENTYL) TETRAETHYLENE JPENTAMINE, N,N'' -DI- (1-METHYLHEPTYL) ETHYLENE DIAMINE AND N1,N3-DI-(1-METHYLHEPTYL) DIETHYLENE TRIAMINE. 